the tuned item was ice king boreas staff wich i converted into leandra staff by using the "base item" menu of MooseEdit, (exploring the data tab it is called _GEN_leandra_staff )
the edited weapon does not support any change of positition in the inventory, if i unequip it , it simply desappear,the same thing occurs if i equip an another weapon from inventory or if i try to move its place on the "bag".

I wonder if it is due to some corrupted heritage with a quest that tell me to trow the original item ( ice king boreas staff ) into a forge(i choosed not to do it) to deliver the white witch.

Thanks you for your (realy fast) answer!